This investigation will be concerned with the study of the sulfated mucopolysaccharide protein complexes (proteoglycans) that we have demonstrated are synthesized and secreted by endothelial cells. Primary cultures and established lines of endothelial cells from rabbit aorta will be used. Attention will be focused particularly on heparin related mucopolysaccharides both as components of the endothelial cell membrane and as species that are secreted into the medium. Proteoglycans will be fractionated by precipitation with various lectins and the structure of the mucopolysaccharide moiety will be investigated; in particular, differences in chain size and in the amount and distribution of sulfate groups between species isolated from different subcellular fractions will be analysed. Immunological studies will be performed with antibodies prepared in goats against the various proteoglycan. The proteoglycans isolated by precipitation with various lectins will also provide the material for the development of affinity chromatography columns that will be used for the study of the interaction of the proteoglycans with different blood components.